Backdoor spending authority in the federal budget is budget authority to incur obligations that evades the normal Congressional appropriations process because it is provided in legislation other than appropriation acts. Spending authority is the technical term for backdoor authority[1], and defined in section 401(c)(2) of the Congressional Budget Act of 1974, as amended, as various types of authority to obligate the United States to make payments, the budget authority for which is not provided in advance in appropriations acts.

Various types of backdoor spending authority include authority to enter into contracts; to incur indebtedness; to make payments (including loans, grants and entitlements) to persons or governments who meet requirements established by law; to allow United States government executive departments and agencies to forgo collection of proprietary offsetting receipts[2]; and to make any other payments (including loans, grants, and payments from revolving funds).

From the perspective of the appropriations committees, funding by these forms of spending authority slips away from their control through legislative back doors. However, the Congressional Budget Act of 1974 gave those committees some control over new borrowing and contract authority.